Put it on the inside and do not but weld it. Remember the floor holds the weight of the fuel tank . One other thing always have a spare in the car. The carriage bolt that holds the spare in holds the fuel tank strap brace up. I have see them rip through the floor with a full tank just relying on the sheet metal. The spare tire helps hold the tank up. The replacement well wedged in from the top is a added support for the well. Just some info you might want to consider.
